[PATCH 1/2] drm/amd/display: increase max surfaces in line with planes and streams

[Melissa Wen]

Hi,

Gentle ping to land the fix for the kernel crash.
If faster, I can send a new version increasing max surfaces to 4 as 
previously discussed.

There are now two bug reports for the same issue:
- https://gitlab.freedesktop.org/drm/amd/-/issues/3693
- https://gitlab.freedesktop.org/drm/amd/-/issues/3594

Best Regards,

Melissa


On 27/09/2024 15:20, Melissa Wen wrote:
> Hi Zaeem,
>
> Thanks for explaining their relationship.
>
> So IIUC, current DM implementation for dc_surface_updates array is 
> wrong, since it's taking MAX_SURFACES (=3) for allocation but 
> MAX_PLANES (=6) as the upper bound of size of the dc_surface_updates 
> array, as you can see in this allocation and after an iteration from 0 
> to `plane_count`:
>
> https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c#L9861 
>
>
> Another question to understand what would be the right fix for the 
> implementation above-mentioned: with the cursor overlay mode, it means 
> we are using one of the overlay planes for this cursor overlay mode 
> (one from the "max_slave_planes") or this cursor plane is an extra 
> plane, which means, for some drivers, one primary plane + two overlay 
> planes + one plane for cursor overlay mode (max 4 planes) ?
>
> BR,
>
> Melissa
>
> On 27/09/2024 14:40, Mohamed, Zaeem wrote:
>> [AMD Official Use Only - AMD Internal Distribution Only]
>>
>> Hi Melissa,
>>
>> MAX_SURFACE_NUM and MAX_PLANES both represent the upper bound of 
>> planes that are supported by HW. It is best to replace 
>> MAX_SURFACE_NUM with MAX_PLANES to remove redundancy. MAX_SURFACES is 
>> used to represent the upper bound of surfaces that can be piped to a 
>> single CRTC. Keep MAX_SURFACES as is to keep stack size down, and 
>> replace MAX_SURFACE_NUM with MAX_PLANES.
>>
>> Thanks,
>> Zaeem
>>
>>
>> -----Original Message-----
>> From: dri-devel <dri-devel-bounces at lists.freedesktop.org> On Behalf 
>> Of Melissa Wen
>> Sent: Wednesday, September 25, 2024 11:37 AM
>> To: harry.wentland at amd.com; sunpeng.li at amd.com; 
>> Rodrigo.Siqueira at amd.com; alexander.deucher at amd.com; 
>> christian.koenig at amd.com; Xinhui.Pan at amd.com; airlied at gmail.com; 
>> daniel at ffwll.ch
>> Cc: amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org
>> Subject: [PATCH 1/2] drm/amd/display: increase max surfaces in line 
>> with planes and streams
>>
>> 091a97e542cf ("drm/amd/display: Fix warning. Set MAX_SURFACES to 3") 
>> reduced the max number of surfaces since, at that time, there was no 
>> use for more. However, HW and driver evolves and there are now driver 
>> versions that allow two overlay planes (max_slave_planes). Moreover, 
>> commit 3cfd03b79425 ("drm/amd/display: update max streams per 
>> surface") states 6 is the max surfaces supported asics can have. 
>> Therefore, update MAX_SURFACES to match MAX_SURFACE_NUM, MAX_PLANES 
>> and MAX_STREAMS.
>>
>> It also addresses array-index-out-of-bounds reported in the link.
>>
>> Link: https://gitlab.freedesktop.org/drm/amd/-/issues/3594
>> Signed-off-by: Melissa Wen <mwen at igalia.com>
>> ---
>>   drivers/gpu/drm/amd/display/dc/dc.h | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/dc/dc.h 
>> b/drivers/gpu/drm/amd/display/dc/dc.h
>> index 3992ad73165b..08b00b263533 100644
>> --- a/drivers/gpu/drm/amd/display/dc/dc.h
>> +++ b/drivers/gpu/drm/amd/display/dc/dc.h
>> @@ -57,7 +57,7 @@ struct dmub_notification;
>>
>>   #define DC_VER "3.2.301"
>>
>> -#define MAX_SURFACES 3
>> +#define MAX_SURFACES 6
>>   #define MAX_PLANES 6
>>   #define MAX_STREAMS 6
>>   #define MIN_VIEWPORT_SIZE 12
>> -- 
>> 2.45.2
>>
>